Kylie explained that (–4x + 9)2 will result in a difference of squares because (–4x + 9)2 = (–4x)2 + (9)2 = 16x2 + 81. which statement best describes kylie’s explanation?

a=kylie is correct.
b=kylie correctly understood that it is a difference of squares, but she did not determine the product correctly.
c=kylie did not understand that this is a perfect square trinomial, and she did not determine the product correctly.
d=kylie determined the product correctly, but she did not understand that this is a perfect square trinomial.